Method of disinfecting water with iodine species

ABSTRACT

A water treatment system and apparatus for producing bacteria- and virus-free water from a bacteria and virus-containing water supply, said apparatus comprising 
     (a) generator means for holding solid elemental iodine and to allow solubilization of said iodine under dynamic aqueous flow; 
     (b) means for feeding a first portion of said water supply to said generator means to produce an aqueous concentrated iodine solution; 
     (c) means for providing a second portion of said water supply; 
     (d) means for providing said aqueous concentrated iodine solution to said second portion of said water supply to provide a blended water supply; 
     (e) storage means for holding said blended water supply to provide said bacteria- and virus-free water; 
     (f) means for measuring water flow of said first and said second portions; 
     (g) means for measuring the pH of said second portion; 
     (h) means for adjusting the pH of said second portion; 
     (i) means for measuring the temperature of said concentrated aqueous solution; and 
     (j) control means for receiving flow data, pH data and temperature data from said means for measuring flow of said first and said second portions, said means for measuring pH of said second portion; said means for measuring temperature of said concentrated aqueous solution and means for adjusting pH of said second portion. The system provides an efficacious way of killing virus under the guidelines and standards set by the USEPA.

This is a division of application Ser. No. 08/701,762, pending filedAug. 22, 1996.

FIELD OF THE INVENTION

This invention relates to a method of disinfecting water with iodinespecies, particularly, hypoiodous acid and dissolved molecular iodine.

BACKGROUND TO THE INVENTION

Iodine has been used for water disinfection on a large scale in thepast. Iodine is used commonly also for its antibiotic (sensu stricto)effects against bacteria, viruses and cysts, as these three pathogensconstitute the most common health risks in maintaining biologically safewater supplies. Traditionally, crystalline iodine is dissolved in waterunder static conditions by the addition of small amounts of KI, whichgreatly enhances the dissolution of the iodine.

Of particular interest in a drinking water context, are those bacteriaresponsible for widespread occurrences and recurrences of intestinalinfections in humans, namely, the coliform family of bacteria, e.g., Ecoli. These bacteria commonly contaminate drinking water supplies whenwaste water containing faecal material spills into a water supply, orwhen excessive anaerobic decay of vegetation in the water supply occurs.In general, the actual inactivation mechanism of the pathogenicity ofboth bacteria, viruses and cysts by iodine is poorly understood.

Poliovirus 1 (Polio 1) is particularly prevalent in third worldcountries, where immunization programs are almost non-existent, andlocal drinking water supplies and sewage waters run side-by-side.

To-date, iodine is generally provided from an iodophor source or as anaqueous solution by the use of KI to aid the dissolution of iodine. Mosttreatments employ pHs lower or higher than about 9.

Dissolved iodine hydrolyzes in aqueous solutions to form hypoiodousacid, HOI, in amounts proportional to the pH of the solution, whereinabove pH 8.5, iodine is present almost exclusively as HOI. Bothdissolved I₂ and HOI possess antipathogenic properties. At pHs 5-7,iodine, as I₂, exhibits antibacterial action and at higher pHs, e.g.7-10, HOI is an efficient virucide. Chang (1) reports that above pH 8,HOI decomposes slowly to form iodide and iodate ions, especially in thepresence of dissolved iodides. Neither iodides nor iodates have beenfound to be germicidal. Further, I⁻ reacts with I₂ to form the highlycoloured I₃ ⁻ ion, which is also ineffectual as a germicide.

Various tinctures of iodine may be generated upon dissolving the solidin organic liquids such as ethanol, acetone, diethyl ether, toluene,p-xylene, benzene and carbon disulphide. Additionally, many organicpreparations of iodine may be generated by reacting appropriate organicswith iodine, e.g., iodoform, methylene iodide. Among the most popularcommercial iodine-organic complexes are the PVP-iodines, iodoforms andpovidone-iodine preparations, which are used as detergents andantiseptics. Most of these compounds exhibit germicidal action upondilution in water, whereupon the iodine is hydrated and released intothe water, usually as molecular iodine. Many biocidal, organic iodinecompounds are commonly referred to as iodophors.

Traditionally, iodine-bearing resins are made by attaching I₂, tri-,penta- and hepta-iodide ions to quaternary ammonium, styrene-divinylbenzene, cross-linked anion-exchange resins. Upon elution with water,the polyiodides and iodine are released from the resin viaanion-exchange mechanisms. These resins are thought to operate on ademand-type basis, where iodine will only be released in the presence ofa germicidal load in the water passing through the resins, by thefollowing mechanisms; (1) iodine release aided by an internal exchangemechanism involving I₂ transfer through a polyiodide intermediate, (2)hydrolysis of iodine on the resin to produce HOI, (3) simple release ofI₂ by the resin-polyiodide combination and/or organic resin matrix.

Berg et al (2) showed that, dissolved, elemental iodine in the presenceof KI to enhance solubility of iodine at a pH=6 and an iodineconcentration of about 2 ppm at 15° C., killed Polio I to the 99.99%level after a 1 minute contact time,. Although this kill-level doescomply with the USEPA (United States Environmental Protection Agency)guidelines, the experimental conditions do not, because the requiredkill must be achieved at 4° C. Additionally, the amount of virus usedwas about 4.13×10⁴ PFU/ml, which is about 2 times more than the USEPAtesting protocol specifies. This reference shows that Polio 1 can beeffectively killed at lower pH than traditionally expected by earlierresearch, that the rates of kill are increased with increasingconcentration of iodine, and that iodine concentration falls with time.

Hsu et al (3) teach that using dissolved elemental iodine in thepresence of KI, pH=7, T=37° C. and an iodine concentration of about 20ppm, Polio 1 can be killed to about the 99.996% level after 10-20minutes contact time. However, the reference also shows that thepresence of iodide ion actually inhibits the rate and amount of viralinactivation. Although the kill ratios meet the USEPA guidelines, theyonly do so at body temperature, and not at the colder temperaturerequired by the USEPA. A viral concentration of about 4.5×10⁵ PFU/ml,which is about 20 times too strong, relative to the USEPA specificationswas used.

Cramer et al., (4) have demonstrated that dilute tincture of iodine, at30 ppm. in contact with Poliovirus Type 3 for 30 minutes, at a pH of 10and T=27° C., kills to about the 99.99999% level. However, althoughUSEPA-required kill ratios were achieved, these were not under thestrenuous conditions dictated by the USEPA testing protocol. Further,unfortunately, the experiments involved about 1×10⁶ PFU/ml of Polio 3which is about 300 times too much.

Taylor and Butler (5) teach that Polio I at 30 μM dissolved, elemental"Iodine", (specification unknown) at 5° C., pH=9 and a 10 minute contacttime kill Polio I to about the 99.8% level. However, the concentrationsof virus or "Iodine" is not given. Further, USEPA kill levels were notmet.

Alvarez et al. (6) show that, at pH=10, T=25° C., with a contact time ofabout 15 minutes, Polio 1 could be killed to the 90-99% level usingabout 1-2 ppm of iodine from a tincture. This reference also shows thatiodine inactivates Polio 1 by affecting the ability of the virus to beabsorbed by host cells. Unfortunately, these conditions did not meet thedesired kill ratios set forth by the USEPA guidelines.

Accordingly, there still remains a need for an efficacious process forkilling viruses, particularly Polio I, that satisfies the USEPAexperimental guidelines and kill standards and which process also killsbacterial to the degree as presently seen in the art.

PUBLICATIONS

1. Chang, S. L., J. Amer. Pharm. Ass., (1958), 47, pp. 417-423.

2. Berg G. et al. Virology (1964), 22, pp. 469-481.

3. Hsu et al. Journal of Epidemiology (1996), 82, 3, pp. 317-

4. Cramer W. N. et al (1976), 48, 1, pp. 61-76.

5. Taylor G. R. and Butler M., J. Hyg. Camb., (1982), 89, pp. 321-328.

6. Alvarez M. E. and O'Brien R. T. Applied & Environmental Microbiology(November 1982), 44, 5, pp. 1064-1071.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an efficaciousprocess for killing bacteria present in drinking water, which processmeets the USEPA guidelines.

It is a further object to provide an efficacious process for killingviruses present in drinking water, which process meets the USEPAguidelines.

It is a yet further object to provide a water treatment system andapparatus which provides the aforesaid two objects of the invention.

Accordingly, in one aspect the invention provides a method ofdisinfecting water to kill bacteria and viruses using iodine speciescomprising hypoiodous acid and iodine in aqueous solution, said methodcomprising treating said water containing said bacteria and viruses witha disinfecting effective amount of said iodine species at a pH selectedfrom 9-10 to provide bacteria and virus-free water.

Preferably, the iodine species concentration is selected from 2-200 ppmand, more preferably, 10-20 ppm. Most preferably, the disinfectingsolution consists essentially of HOI and I₂.

By the term iodine species as used in this specification is meant,collectively, dissolved molecular iodine and hypoiodous acid speciespresent over the pH range 9-10. The ppm concentrations herein refer tothe concentrations of these species determined as iodine species whichare chemically free to react with pathogens, i.e. the total amount of I₂and HOI.

We have found that a suitable contact time ranges from about 1 to 30minutes at pH 9-10, and depends on the temperature and iodine speciesconcentration. In the dynamic process aspect of the present invention, asuitable contact time is about 10 minutes at a pH of 9.5, concentrationof 10-15 ppm and temperature of between 12°-18° C.

In a preferred aspect of the invention, the efficacious iodinespecies-containing water is prepared by blending a minor amount ofrelatively highly concentrated iodine species solution with a majoramount of untreated water under the treatment conditions as hereinbeforedefined.

Most preferably, we have found that a most satisfactory method ofattaining a suitably iodine species-concentrated aqueous solution isunder dynamic aqueous flow conditions wherein a flow of water is passedthrough elemental iodine in the form of flakes at such a rate as toproduce a desired concentration, preferably 100-500 ppm. Addition ofthis concentrated solution to the main water supply to be treated is ata rate as to produce the desired 10-20 ppm iodine species concentration.

In a further aspect, the invention provides a water treatment system forproducing bacteria- and virus-free water from a bacteria- andvirus-containing water supply, said system comprising

(a) generator means for holding solid elemental iodine and to allowsolubilization of said iodine under dynamic aqueous flow;

(b) means for feeding a first portion of said water supply to saidgenerator means to produce an aqueous concentrated iodine solution;

(c) means for providing a second portion of said water supply;

(d) means for providing said aqueous concentrated iodine solution tosaid second portion of said water supply to provide a blended watersupply;

(e) storage means for holding said blended water supply to provide saidbacteria- and virus-free water;

(f) means for measuring water flow of said first and said secondportions;

(g) means for measuring the pH of said second portion;

(h) means for adjusting the pH of said second portion;

(i) means for measuring the temperature of said concentrated aqueoussolution; and

(j) control means for receiving flow data, pH data and temperature datafrom said means for measuring flow of said first and said secondportions, said means for measuring pH of said second portion; said meansfor measuring temperature of said concentrated aqueous solution andmeans for adjusting pH of said second portion.

Most preferably, excess iodine species may be readily removed from thetreated water by means of iodine and/or iodide strippers.

BRIEF DESCRIPTION OF THE DRAWING

In order that the invention may be better understood, a preferredembodiment will now be described by way of example only with referenceto the drawing, wherein FIG. 1 represents a schematic flow diagram of amethod, apparatus and system according to the invention, and whereindotted lines denote electrical connections.

DESCRIPTION OF PREFERRED EMBODIMENT

With reference to FIG. 1, the system comprises a water feed inletconduit 10 which feeds inlet water to a preconditioner 12. The incomingsource water is, typically, a municipal drinking water, hereinafterreferred to as the "main flow" which enters the system at, typically,ambient temperature. However, the system of the invention is designed toaccept water also at other temperatures of between 0°-40° C.Preconditioner 12 is an optional feature and contingent upon the qualityand chemistry of the source water and preconditioner may includeprefilters, as well as water softeners or phenol scrubbers.

Main flow water exits preconditioner 12 and passes throughout the systemthrough conduit 14. A pressure gauge 16 measures the pressure of theincoming source water, which pressure is monitored by a computerizedcontroller 18, such that the pressure never exceeds the operatingconditions, typically, 45-100 psi. If the pressure limits are exceeded,the system shuts down. A flow meter 20 measures the flow of the mainflow and provides this information to controller 18. The operation ofthe system of this embodiment is controlled to provide a flow rate valueselected from between 0-12 USGPM.

Conduit 14 leads to a carbon pre-filter 22 to remove unwanted halogen,trihalomethane and organic residuals and to a particle filter 24 of,typically, wound cotton providing greater than 5 micron filtration toremove fine mineral, organic and carbon particles. Downstream of filter23 is a pH control station shown generally as 23 having an acid and/orbase reservoir 26 and a static mixer 28. Reservoir 26 provides acid orbase as the case may be under the control of controller 18 upon pHinformation provided by a pH meter 30. The preferred base for additionis sodium hydroxide and is mixed with the main flow by means of thestatic, in line mixer 28.

The pH adjusted-main flow exits static mixer 28 and a portion of themain flow is diverted through a iodine-generator and iodine-sensor loopshown generally as 31 comprising a side conduit 32, pump 34, flow meter36, two iodine generators 38 in series and iodine sensor 40. The iodinesensor at the wavelength used detects total free iodine, i.e. both I₂+HOI. Iodine generators 38 comprise PVC canisters which containcrystalline iodine and have water-entry and liquor-exit holes (notshown). The resultant concentrated iodine solution, herein called"liquor" is blended back into the main flow at a carefully monitored andcontrolled rate by controller 18. The temperature of the liquor ismeasured by a thermometer 42 and reported to controller 18 as is the pHof the blended main flow in conduit 14 as measured by a pH meter 44.

Blended main flow is fed through a cyst filter 46 to residence contacttank 48. Cyst filter 46 removes particles and cysts (e.g protozoans,emoebas) having a diameter greater than about 1 micron. From residencetank 48, conduit 14 passes the treated blended main flow water to anactivated carbon iodine stripper 50, which effectively removes any freeiodine species e.g. molecular iodine and hypiodous acid from the blendedmain flow. Treated water from iodine stripper 50 is passed to an iodideion-exchange stripper 52, containing e.g. Purolite resin. Iodine-free,disinfected potable water is discharged from stripper 52 for subsequentuse.

The following description illustrates a typical process according to theinvention using the apparatus described hereinabove.

Municipal water is fed through inlet conduit 10 through preconditioner12 at a flow rate selected from 4.5-12 USGPM, pH 5-9, temperature 10° C.and pressure of 85 psi. as measured by pressure gauge 16 under theinfluence of computer controller 18. Main flow water enters and leavescarbon filter 22 wherein the pH of the main flow is increased by 1-2 pHupon passing therethrough. The amount of acid or alkali, generallysodium hydroxide, delivered to the main flow as 10 molar sodiumhydroxide is such that the iodinated blend water as measured by pH meter44 has a pH of 9.5±0.2 pH. The amount of main flow diverted through loop32 is controlled by controller 18 and where upon controller 18 instructspump 34 to deliver an appropriate flow to iodine generators 38 as togenerate sufficient aqueous iodine species for the production of a finalconcentration of 10 ppm. free iodine in blended main flow line 14. Atypical flow through loop 32 is 0.08-1.46 USGPM (166 ml./min.-2806ml./min.) to provide a resultant concentrated iodine value of 100-500ppm. by passage of the side stream through generators 38 each containing1.75 kg. pure, crystalline iodine in flake form. Flow rate, temperatureand pre-determined solubility curves enable the correct iodineconcentration to be generated as determined by sensor 40. Iodine sensor40 is, prefereably, an in-line, spectrophotometric flow-through cellwith a dedicated detector tuned to 460 nm for the detection of colourediodine species, chiefly hypoiodous acid. The main function of sensor 40is to inform controller 18 when the iodine concentration of the liquordrops below about 130 ppm. Digital thermoprobe monitor 42 measures thetemperature of the liquor as it emerges from sensor 40. The temperaturevalue is fed to controller 18 where it is applied to an equationgoverning the liquor/pump rate, such that the concentration of theliquor and, hence, the blended flow is suitable. It is most preferredthat sensor 40 is located within loop 32 as shown in view of thelikelihood that the system may sit idle for hours or days, whereuponiodine crystals and the liquor in immediate contact therewith mayequilibrate to ambient temperature--which may be different from that ofthe incoming source water. If temperature sensor 42 is placed in conduit14 upstream of loop 32, an incorrect amount of iodine liquor could befed into main line 14 upon blending. In the present embodiment, locationof the temperature probe accounts for any gradual cooling or warming ofthe liquor within the iodine-generator loop, such that correspondingchanges in liquor concentration as the temperature of the systemre-equilibrates the temperature of the incoming source water. pH meter44 reports to controller 18 to instruct pH control station 23 to add theappropriate amount of sodium hydroxide, such that the pH of the blendedflow after iodination is 9.5.

The iodinated, blended flow is controlled to provide a free iodineconcentration selected between 10-20 ppm. The process of the invention,as hereinabove described, operates under a residence time for theiodinated water of 10 minutes to ensure mortality of any viruses andbacteria within the main flow, caused mainly by the presence of HOI atpH 9.5. Passage of the blended iodinated main flow through iodinestripper 50 raises the pH of the main flow by about 1-2 pH units. Theactivated carbon converts some of the available free molecular iodine toiodides. Passage of the resultant solution through iodide stripper 52causes the pH of the discharge water to drop by 3-4 units. Trace amountsof molecular iodine (2-4 ppm) may also be removed by the ion exchangeresin. The acceptable value for total iodine concentrations, at thisstage, is 40 ppb or less. A resultant pH of 5-7 for the discharged wateris most acceptable.

Controller 18 is a sophisticated pre-programmed computer capable ofmonitoring and controlling the desired aspects of the process within thesystem by communicating with pH, temperature, pressure, flow and I₂sensors placed at strategic locations, as hereinbefore described.

In the embodiment described herein, the controller is accessible via auser operated keypad, such that system parameters may be changed tofine-tune the system when installation occurs, or in the event of asystem error, to effect shutdown. Certain operator-defined systemparameters may be altered from original input values to compensate forvariation in physical and chemical conditions encountered in the field,e.g., pressure, flow rates. Other parameters may be changed by the userto reflect the specific needs of the duty, e.g., iodine concentrationand pH of output water. By sensing the temperature and pH of theincoming source water, the controller is able to adjust the pH of thewater to about 10.0, such that the dissolution of the iodine thenbecomes temperature dependent only, and the concentration of iodine inmain line 14 is about 10 ppm. Controller 18 is pre-programmed withtemperature vs solubility curves for iodine, such that the appropriateamount of liquor at the correct iodine concentration is delivered intothe main flow. The dissolution of iodine effects a pH drop of about 0.5pH units while the pH of water in the main line will be adjusted toabout 9.5.

EXAMPLES Example 1

An evaluation of the virucidal activity on Poliovirus Type I of theprocess of the invention, which process provides a 10 ppm iodinated testwater, pH 9.5 at 4° C. at a 10 minute exposure, was conducted under thefollowing protocol.

100 ml. each of (i) distilled water at pH=7.25, (ii) municipal Dartmouth(Nova Scotia, Canada) water adjusted to pH=9.5; and (iii) Test Waterwere dispensed in glass bottles and chilled to refrigerationtemperature. Stock Poliovirus Type 1 (P1), the test virus, in a 10 μlaliquot containing approximately 2.6×10⁶ plaque-forming units (PFU) wasadded to each sample to yield a titer of 2.6×10⁴ PFU/ml in each testsample. Each sample was incubated 10 minutes in a refrigerator, withoccasional mixing, subsequently 2 ml. of 0.1% sodium thiosulfatesolution was added to each sample to stop further action of iodine andresidual virus infectivity in each of the solutions was determined byplaque assay on 6-well BGMK (Buffalo Green Monkey Kidney cells)monolayer cultures.

Example 2

A similar evaluation to that of Example 1 was conducted on test water(2) treated according to the invention at a pH of 10.10, at 10 ppm I₂ at12°-14° C. for 10 minutes.

100 ml. each of (i) distilled water at pH 7.25, (ii) Dartmouth wateradjusted to pH=9.5 and (iii) test water (2) were dispensed in glassbottles and left to stand at about 12°-14° C. Stock Poliovirus Type 1(P1), the test virus, in a 10 μl aliquot containing approximately2.6×10⁶ plaque-forming units (PFU) was added to each sample to yield atiter of 2.6×10⁴ PFU/ml in all three test samples, respectively. After 1minutes of incubation at 12°-14° C. with occasional mixing, 2 ml. of0.1% sodium thiosulfate solution was added to each sample to stopfurther action of iodine and residual virus infectivity in each of thesolutions was determined by plaque assay on 6-well BGMK monolayercultures.

                                      TABLE 1                                     __________________________________________________________________________    Table 1 presents bactericidal and virucidal results from selected             literature.                                                                                           Contact time  Iodine                                  Reference                                                                          Pathogen                                                                              pH    T °C.                                                                       (min.)                                                                              Iodine source                                                                         conct. (ppm)                                                                        % Kill                            __________________________________________________________________________    Bacteria                                                                           faecal  7-8.5 20°                                                                         30    ?       1-8   10                                     coliform                                                                      E. coli 6, 7.5                                                                              5, 20, 35°                                                                  30    ?       1-10  100                               Virus                                                                         2.   Polio 1 6     15°                                                                         20    elemental I.sub.2 + KI                                                                .2-2  99.99                             3.   S. abortivoequina                                                                     7     37°                                                                         10-20 elemental I.sub.2 + KI                                                                .1-20                                        E. coli                                                                       H. influenzae                                                                 f2 bacteriophage                                                              Polio 1                                99.996                            4.   Polio III                                                                             4, 6, 7, 10                                                                         27°                                                                         30    tincture of iodine                                                                    30    99.99999                          5.   Polio 1 5, 7, 9                                                                             5°                                                                          10    elemental I.sub.2                                                                      8    99.9                                   f2 bacteriophage                                                         6.   Polio 1 5, 8, 6, 7, 10                                                                      25°                                                                         15    tincture of iodine                                                                    .8-2.5                                                                              90-99.9                           __________________________________________________________________________

Table 2 presents the efficacy of iodination according to the process ofthe present invention under the stated conditions against K.pneumoniabacterium. The results show that iodinated water at the relatively highpH of 9.5 is as satisfactory as the expected iodination at lower pH 6.The results show that the USEPA guidelines are met, in terms ofrequisite kill levels at 4° C. against the virulent K.pneumoniabacterium.

                                      TABLE 2                                     __________________________________________________________________________    Bacteria                                                                                                 Infusion                                                                           Recovered                                                                            % Kill (rel. to                        Sample                                                                             (I.sub.2)                                                                          pH T  t   Species                                                                              (pfu/ml)                                                                           (pfu/ml)                                                                             control)                               __________________________________________________________________________    Iodinated                                                                          2 ppm                                                                              5.90                                                                             4° C.                                                                     10 min.                                                                           K pneumonia                                                                          2.74 × 10.sup.6                                                              <10    99.9996                                water                                                                         Iodinated                                                                          4 ppm                                                                              5.99                                                                             4° C.                                                                     10 min.                                                                            K. pneumonia                                                                        2.74 × 10.sup.6                                                              <10    99.9996                                water                                                                         Iodinated                                                                          8 ppm                                                                              6.07                                                                             4° C.                                                                     10 min.                                                                            K. pneumonia                                                                        2.74 × 10.sup.6                                                              <10    99.9996                                water                                                                         Distilled                                                                          0 ppm                                                                              9.48                                                                             4° C.                                                                     10 min.                                                                            K. pneumonia                                                                        3.60 × 10.sup.7                                                              too numerous                                                                         confluent                              water                           to count                                                                             overgrowth                             Iodinated                                                                          10 ppm                                                                             9.49                                                                             4° C.                                                                      5 min.                                                                            K. pneumonia                                                                        2.60 × 10.sup.7                                                              2.1 × 10.sup.1                                                                  99.999942                             water           10 min.         0                                             Iodinated                                                                          10 ppm                                                                             9.49                                                                             4° C.                                                                      5 min.                                                                            K. pneumonia                                                                        3.60 × 10.sup.7                                                              9.5 × 10.sup.1                                                                 99.981                                 water           10 min.         0                                             __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    Table 3 presents the efficacy of iodination according to the process of       the present                                                                   invention under the stated conditions against Poliovirus I. The results       show the efficacy                                                             of the iodination process according to the invention against Polio 1. The     process of the                                                                invention closely follows the USEPA test protocols and exceeds requisite      kill ratios.                                                                  Viruses                                                                                                   Infusion                                                                           Recovered                                                                            % Kill (rel. to                       Sample                                                                              (I.sub.2)                                                                          pH T   t   Species                                                                             (pfu/ml)                                                                           (pfu/ml)                                                                             control)                              __________________________________________________________________________    Test Water 1                                                                        10 ppm                                                                             9.5                                                                              4° C.                                                                      10 min.                                                                           Poliovirus 1                                                                        2.6 × 10.sup.4                                                               2      99.992                                Dartmouth                                                                           0 ppm                                                                              9.5                                                                              4° C.                                                                      10 min.                                                                           Poliovirus 1                                                                        2.6 × 10.sup.4                                                               2.53 × 10.sup.4                                                                2.700                                 water                                                                         Distilled                                                                           0 ppm                                                                              7.25                                                                             4° C.                                                                      10 min.                                                                           Poliovirus 1                                                                        2.6 × 10.sup.4                                                               2.42 × 10.sup.4                                                                6.930                                 water                                                                         Test Water 2                                                                        10 ppm                                                                             10.00                                                                            12° C.                                                                     10 min.                                                                           Poliovirus 1                                                                        2.6 × 10.sup.4                                                               0      100.000                               Dartmouth                                                                           0 ppm                                                                              9.5                                                                              12° C.                                                                     10 min.                                                                           Poliovirus 1                                                                        2.6 × 10.sup.4                                                               2.53 × 10.sup.4                                                                2.700                                 water                                                                         __________________________________________________________________________

Although this disclosure has described and illustrated certain preferredembodiments of the invention, it is to be understood that the inventionis not restricted to those particular embodiments. Rather, the inventionincludes all embodiments which are functional or mechanical equivalenceof the specific embodiments and features that have been described andillustrated.

We claim:
 1. A water treatment system for producing bacteria- andvirus-free water from a bacteria- and virus-containing water supply,said system comprising(a) generator means for holding solid elementaliodine and to allow solubilization of said iodine under dynamic aqueousflow; (b) means for feeding a first portion of said water supply to saidgenerator means to produce an aqueous concentrated iodine solution; (c)means for providing a second portion of said water supply; (d) means forproviding said aqueous concentrated iodine solution to said secondportion of said water supply to provide a blended water supply; (e)storage means for holding said blended water supply to provide saidbacteria- and virus-free water; (f) means for measuring water flow ofsaid first and said second portions; (g) means for measuring the pH ofsaid second portion; (h) means for adjusting the pH of said secondportion; (i) means for measuring the temperature of said concentratedaqueous solution; and (j) control means for receiving flow data, pH dataand temperature data from said means for measuring flow of said firstand said second portions, said means for measuring pH of said secondportion, said means for measuring temperature of said concentratedaqueous solution and means for adjusting pH of said second portion.
 2. Asystem as defined in claim 1 further comprising means for removingiodine and iodide ions from said bacteria- and virus-free water.
 3. Awater treatment system for producing bacteria- and virus-free water froma bacteria- and virus-containing water supply, said system comprising(a)a generator constructed and adapted for holding solid elemental iodineand to allow solubilization of said iodine under dynamic aqueous flow;(b) delivery means constructed and adapted for feeding a first portionof said water supply to said generator to produce an aqueousconcentrated iodine solution; (c) delivery means constructed and adaptedfor providing a second portion of said water supply; (d) delivery meansconstructed and adapted for providing said aqueous concentrated iodinesolution to said second portion of said water supply to provide ablended water supply; (e) storage means constructed and adapted forholding said blended water supply to provide said bacteria- andvirus-free water; (f) measurement means constructed and adapted formeasuring water flow of said first and said second portions; (g)measurement means constructed and adapted for measuring the pH of saidsecond portion; (h) adjustment means constructed and adapted foradjusting the pH of said second portion; (i) measurement meansconstructed and adapted for measuring the temperature of saidconcentrated aqueous solution; and (j) control means constructed andadapted for receiving flow data, pH data and temperature data from saidmeans for measuring flow of said first and said second portions, saidmeans for measuring pH of said second portion, said means for measuringtemperature of said concentrated aqueous solution and means foradjusting pH of said second portion.